1. Field of the Invention
The present invention relates, in general, to a laser projection display and, more particularly, to a laser projection display, which can correct image distortion without requiring a separate image distortion correction means.
2. Description of the Related Art
A Laser Projection Display (LPD) is a device which is connected to a small-sized handheld device, for example, a mobile phone, a Personal Digital Assistant (PDA), or a mini-laptop display, and which is adapted to show a magnified image on a screen installed on, for example, a wall or ceiling. When such a small-sized LPD module is provided, multiple content items stored in a mobile phone or PDA can be easily magnified and viewed anywhere. Accordingly, Digital Multimedia Broadcast (DMB) images, which inconvenience the user due to the small screen when viewing the DMB images using a mobile phone or PDA, movies, education broadcasting, game content, etc. can be viewed as magnified images. Even though a projector is not necessarily connected to a notebook computer, presentation can be easily performed through a PDA, etc.
When using a light source for emitting point-type light beams, the display scans the light beams across a screen while moving the light beams in vertical and horizontal directions using two reflective mirrors, that is, a galvano mirror and a polygonal mirror. Further, when using a light source for emitting line-type light beams, the display scans the light beams across a screen while moving the light beams in a horizontal direction using a single reflective mirror, that is, a polygonal mirror.
An example of such a display is shown in FIG. 4.
As shown in FIG. 4, a conventional display 10 includes a light source 11, an illumination lens 12, an optical modulator 13, a color mixer 14, a projection lens 15, a galvano mirror 16, a polygonal mirror 17, and a distortion correction lens 18.
The light source 11 emits a monochromatic light beam, or red, green and blue light beams, each having a predetermined wavelength.
The illumination lens 12 condenses the light beams emitted from the light source 11 on the optical modulator 13, independently with respect to respective wavelengths, and includes a plurality of lenses, such as a diverging lens, a collimating lens, and a cylindrical lens.
The optical modulator 13 functions to modulate the condensed light beams and transmit the modulated light beams to the color mixer 14. If light beams are point-type light, a reflective optical modulator is used, whereas, if light beams are line-type light, a diffractive optical modulator is used.
The color mixer 14 focuses light beams, diffracted as 0th-order and ±1st-order diffracted light beams by the optical modulator 13, and mixes the diffracted light beams.
The projection lens 15 projects the light beams mixed by the color mixer 14 both on the galvano mirror 16 and on the polygonal mirror 17. The light beams, reflected from the galvano mirror 16 and the polygonal mirror 17, are scanned across the screen 19 while moving in vertical and horizontal directions due to respective mirrors, thus displaying an image.
In this case, since each of the reflective surfaces of the polygonal mirror 17 for reflecting light beams is planar, the distances from the reflective surface to the screen 19 are different at respective different points, thus image distortion may occur in the image displayed on the screen 19, as shown by the dotted line in the drawing. In order to prevent such image distortion, a distortion correction lens 18 is interposed between the polygonal mirror 17 and the screen 19 in the prior art.
However, the conventional display 10 having the above construction is problematic in that the distortion correction lens 18, which is a separate correction means, must be interposed between the polygonal mirror 17 and the screen 19 so as to correct image distortion, so that the number of components increases, and space for the installation of the distortion correction lens is required, thus the size of the display 10 itself increases.